Scanning X-ray Fluorescence Microanalysis of Phosphorites from the Jeirud Formation, Iran

Articles in Press

Document Type : Research Paper

Authors

1 Department of Geology, Payame Noor University, Tehran, Iran

2 Department of Earth Sciences, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada

Abstract

The phosphorite deposits of the Upper Devonian Jeirud Formation in the Central Alborz, Iran, represent a significant resource within the extensive Tethyan phosphate belt, interpreted as having precipitated in a shallow marine setting influenced by upwelling and anoxic bottom waters. This investigation utilizes high-resolution micro-X-ray fluorescence (µ-XRF) spectrometry to conduct a detailed, spatially resolved analysis of elemental distributions, paragenetic mineralogy, and multi-stage diagenetic pathways within these sedimentary rocks. Comprehensive elemental mapping definitively identifies fluorapatite as the predominant phosphate mineral, manifesting in two principal modes: (i) reworked, rounded to sub-rounded peloids and intraclasts, and (ii) microcrystalline cement. The µ-XRF data provide unequivocal evidence for a key diagenetic overprint involving the partial to complete oxidative replacement of primary phosphate phases by iron (oxyhydr)oxides. Concurrently, the technique facilitates the precise identification of accessory mineralogy, including euhedral pyrite (confirmed via strong Fe–S spatial correlation) and Ti-bearing phases such as rutile or titanite. Quantitative spot analyses reveal significant enrichment of rare earth elements (REEs) within the fluorapatite lattice. Critically, a robust linear correlation between quantitative µ-XRF-derived concentrations and conventional bulk ICP-OES data from paired samples validates the µ-XRF methodology as a highly accurate, reliable, and non-destructive alternative for quantitative geochemical characterization of phosphorites. The study establishes µ-XRF as a powerful tool for deciphering complex paragenetic sequences, elucidating primary sedimentary versus diagenetic textures, and reconstructing post-depositional alteration histories, thereby offering significant utility for both academic research and mineral resource evaluation of phosphate deposits.

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Article Title [Persian]

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Geopersia

Articles in Press, Accepted Manuscript
Available Online from 03 May 2026

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History

  • Receive Date: 01 January 2026
  • Revise Date: 23 February 2026
  • Accept Date: 03 May 2026

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